A magnetic levitation system enables to suspend an object in a non-contact manner and to use in a special environment such as in vacuum or in a clean room where no evaporation of lubricant is permitted because of low vibration and noise due to mechanical abrasion as well as no need for lubrication.
Magnetic levitation methods include a repulsion type for using a repulsion force of magnets, an attraction type for utilizing an attraction force between a magnet and a ferromagnetic member.
FIG. 17 (a) illustrates how a ferromagnetic member 11 disposed between a pair of electromagnets 10 is suspended in a non-contact manner between the electromagnets by attracting magnetic forces of the upper and lower electromagnets 10. The position of the ferromagnetic member 11 in the vertical direction can be held stably by controlling currents to be supplied to the upper and lower electromagnets 10 that result in adjusting magnetic forces generated by these electromagnets 10.
If any external force is applied to the ferromagnetic member 11 in perpendicular to the direction of disposition of the pair of the electromagnets 10 as illustrated in FIG. 17 (b), the ferromagnetic member 11 suspended in a non-contact manner moves (laterally) in the direction that is pushed. At this instance, as illustrated in FIG. 18, a force including a component of an attracting force B as well as a component of a recovering force A that attempts to recover the lateral movement to the original position act at the edge of the ferromagnetic member 11 extending outwardly from the electromagnets 10. This is known as an “edge effect”.
The ferromagnetic member 11 tends to move laterally in the opposite direction to the lateral movement upon receiving the recovering force A, thereby receiving again the recovering force by the edge effect. As a result, the ferromagnetic member 11 repeats vibration in the lateral direction.
As disclosed in the Patent Document 1 below, the vibration in the lateral direction is difficult to converge because no attenuation acts on the ferromagnetic member 11 that is suspended in a non-contact manner.